Electric furnace



. 1,580,511 G. M. LITTLE ELECTRIC FURNACE Filed March 24, 1324 April 13 1926.

WITNEssEs: INVENTOR @.mw CEQ/QefZL/W@ Patented Apr.

UNITED STA GEORGEM. LITTLE, 0F PITTSBUR ELECTRIC MANUFACTURING C GH,rENNsYLvANIA, Ass'IGNOR To WESTINGHOUSE OMPANY, A CORPORATION or PENNSYLVANIA.

ELECTRIC FURNACE.

Application led March 24, 1924. Serial No. 701,287.

To all whom t may concern:

'Be it known that I, GEORGE M. LITTLE,

a. citizen of the United dent of Pittsburg and State of Pennsylvania,

a new and useful Improvement in gheny vented States, and a. resithe county of Alle- 'h, in

have 1n- Electric Furnaces, of which the following is a speciiication.

invention relates to electric 'furnaces to electric-resistance fur- The object of my invention is to provide radiant, electric-heating- In practicing my invention, .I provide a said walls being Aprovided furnace Electric-heatingfunit structures,

an open-sided casing and located within said casing,

therein. y

Means vare provided for each heating-unit view, in vertical section,

a view, in vertical section,

in longitudinal section, -umt structure illustrating "A furnace structure 11, which is illus- End walls (not roof portion 12/and each composed of a plublocks of a suitable heatand particularly naces.

a furnace that shall embody a plurality of quicklyeremovable, 15 unit structures located outside of the furvnace structuredtself and effective to heat the furnace chamber substantially uniformly and permit of easy and quick exy change.

plurality of furnace walls enclosing a furnace chamber, with openings therethrough located substantially uniformly around the chamber.

eac-h comprising` a heating unit operatively engage the furnace walls and cover the openings 0 structure to permit of substantially airtight engagement with the furnace walls.

In the .single sheet of drawings, Figure 1 is a ,35 through-an electric furnace embodying my invention,

Fig. 2 yis through a modified form of electric furnace embodying my invention, and 40 Fig. 3 is a. view,

through aheating `particularly the construction of the heating element.

trated schematically only in Fig.v 1 of the drawing, comprises a a floor portion 13 rality of bricks or .insulating refractorymaterial usually employed in the art.

illustrated)A are provided to co-operate with the roof and the ioor main consideration portions to enclose-a furnace chamber 14, of any suitable or desired contour and dimensions and here illustrated as substantially rectangular in lateral section.

A front opening 15 is provided in the furnace structure 11 and is normally closed by a door member 16, of any suitable or desired construction, that is suspended by al spective openings may be of any suitable length in the longitudinal direction of the furnace. A substantially vsimilar opening 26 is provided in the side ofthe furnace substantially opposite to the door opening 15 and this may be of any desired longitudinal extent.

The opening 24 is normally closed by a heating-unit structure comprising an open bottom casing 27 that is composed of a plusol rality of bricks or blocks of a suitable hightemperature-resisting refractory material usually employed in the art a. heating compartment 28. The normally open side ofthe casing 27 is closed by a yrefractory diaphragm or plate 29, which may be of graphite or of carborund'um, the

being that it shall withstand relatively high temperatures Without serious oxidation thereof and protect a reand enclosing sistor member of carbonaceous material located in the compartment 2S. The open side Aof the casing may be provided With inwardly extending flange portions 30 and31, respectively, to provide supporting means for the plate 29.

A heating element for the heating-unit structure hereinbefore described comprises a plurality of iiat and relatively thin plates 32 (see Fig. 3) that are spaced apart by a plurality of relatively small blocks 33 of electric-conducting refractory material located closely adjacent to the open side of the casing. A plurality of smaller blocks 34 serve as spacers between the adjacentvplates for the other edge of the plates and are, therefor, located adjacent to the other edge portion thereof and away from `the open side of the casing.

The assembled set of plates 32 and the interposed current-conducting blocks 33 and the blocks 34, have located at the ends thereof, contact plates 35 and 36, respectively, the outer surfaces of which are operatively engaged by the inner ends of elongated, refractory, terminal electrodes 37 and 37a, respectively, that extend through the opposite' end walls of the casing 27. lWater cooled, metal terminal members 38 and 39 are in operative engagement with the outer tapering ends of the electrodes 37 and 37 a.

Means for'resiliently compressing the assembled refractory plates 32, the interposed blocks and the elongated electrodes, comprise springs 41 and 42 that are located between adjusting screws 43l and 44 and plates'45 and 46, of electric-insulating material that respectively operatively engage the 'outer surface of the terminal members 38 and 39. While I have -illustrated and described a specific embodiment of resilient compressing means, I do not desire to be limited thereto, as any suitable means of this type may be employed. ,f The hereinbefore described construction of heating element is more particularlyv disclosed and claimed in my co-pending application, Serial No. 598,318, filed November, 1st, 1922, and assigned to the Westinghouse Electric & Manufacuring Company. The heat of the heating element is radiated Y against the refractorydiaphragm which, in

turn, radiates its heat into the furnace chamber.

Means for providing a substantially airtight joint between the heating-unit structure and the roof portion of the furnace may comprise extended angle-bar members 47 and 48 that have one leg thereof secured to the casing 27, and that have the other leg eX- ltend into grooves 49 and 51 provided in the roof -portion of the furnace. A quantity of sand may be'located in the grooves 49 and 51 and, as the angle-bar members'are provided around the entire periphery of the casing 27, a substantially air-tight joint will Abe ensured.

A hook member. 52 is provided in the top of the casing 27 to permit of easily and quickly removing the heating-unit structure whenever this becomes necessary. j

A heating-unit structure is iprovided for the side opening 26 and isof substantially the same construction as hereinbefore described, comprising a casing 53 having anV openl side that is located adjacent to the opening 26. A diaphragm 54 is provided and a heating element is located within the open-sideV casing 53, of v substantially the surface upon which is secured a plate 55,. of metal, upon which the casing 53, having a correspondingly inclined bottom surface may rest, and be caused to closely approach the outer edges of the roof and bottom portions of the furnace structure and thereby effect a substantially air-tight joint.

A heating-unit struc-ture 56, of the carwheel type, is provided for the lower opening 25 of the. furnace structure and comprises an open-top casing 57 of a suitable refractory, high-temperature-resistant mate-l rial, that is located upon a truck structure 58 built up in the usual manner to co-mprise aplatform and wheeled axles. A plurality of spaced rails 59 and 60 are provided upon which the -ca-r may be moved into its proper operative position beneath the furnace structure.

Means for providing an air-tight joint comprise members 61 and 62 of trough form in lateral section that are secured against the stop edge portions of the casing 57 in combination with bar members 63 and 63a that are mounted in the floor portion 13 1n such position as to extend into the respective trough portionsI 61 and 62. `When the trough portions are filled with sand, a substantially air-tight joint is provided between the heating-unit structure 56 and the furnace structure 11.

A diaphragm 64 is located in the heating unit structure 56 immediately adjacent to the opening`25, anda heating element, sub'- Istantially of the same type as 'hereinbefore The furnace structure 65 hasa plurality 1 of spaced bottom openings 69 and 71, re,- spectively, that are K mediate portion 72 that is built up of-a spitable refractory heat-insulating and hightemperature-resisting material. The structure 65 is provided also with suitable end portions, not Shown.

A mass 73, of metal to beheat treated, l

may be moved into and removed from a furnace chamber 74 provided bythe superseparated by an interor desired length in longitudinal extent and is normally closed by a heating-unit structure 77 of the car-Wheel type. The construction ofthis heating-unit structure 77 is substantially the same as that hereinbefore described for the heating-unit structure 56.

in Fig. l' of the drawing and hence it is believed that no further detailed description thereof is necessary. f

A. heating-unit structure 78 is provided for the opening 7l and is of substantially the same construction as hereinbefore described for the structure 56.

It is, of course, understood that the lengths of the heating-unit structures longitudinally of the furnace, are such as to extend slightly beyond the respectivev openings which are covered thereby, so that the heating elements 'located in the respective heating-unit structures Will be substantially co-extensive With the dimensions of the respective openings. If small metal objects are to be heat treated in the furnace structure 11, illustrated in Fig. 1 of the drawing, it may be necessary to provide a suitable' refractory plate for the Hoor thereof, although this furnace has been developed more particularly for the heat treatment of relatively large metal members which may rest upon those portions of the floor portion 13 that are provided in the furnace structure and, therefore, require no other support. l

The respective heating elements are energized by suitable supply-circuit conductors (not shown) thatv are electrically connected to the metal terminal members 38 and 39 and to a suitable source of supply ,of electric energy. The dierent heating elements may be separately connected to the source of supply of electric energy or all of the heating elements may be connected in seriescircuit. relation relatively to each other, as may be found convenient or desirable.

As all of the heating elements comprise refractory members that are subject to oxidation, they must necessarily be replaced or renewed from time to time and if, for instance, the vtop heating-unit structure in Fig. l requires replacement, it is only neces sary to disconnect the' supply-circuit conductors connected to the metal terminal members and lift the heating-unit structure from its normal position on the top of the furnace. new heating-unit structure may be built up in, advance and may be placed -iied form of furnace illustrated in on the furnace structure immediately after the removal of the other heating structure and will be ready for operation as soon as the supply-circuit conductors have been connected to the terminal members.

Substantially the same process may be employed for the replacement of the side heating-unit structure comprising the casing 53. The bottom heating-unit structures Will, of course, be moved out from under the furnace structure on the rails provided for that purpose after the disengagement of the supply-circuit.

conductors, and a new heatingmnit structure may easily and quickly be moved into proper operative position under the furnace structure.V The same method of operation may bev followed for the bottom heating-unit structures that are used alone in the modi- Fig. 2 of the drawings. Y

The plurality of openings'provided in the respective furnace structure permits of em-v ploying a plurality of heating units that are distributed substantiallyl uniformly around'the outside ofthe furnace structure and of the furnace chamber, and substantially uniform heating of a mass of `material located Within the furnace chamber is easily and quickly effected by the heat, radiated into the chamber and against a mass of material located therein.`

It isfurther obvious that the amount of energy translated into heat in the respective heating-unit structures may be varied, if necessary or required, in accordance with the shape of a mass of material located Within the furnace chamber and to` be heated therein.

Various modifications and changes may be made Without departing from the spirit and scope of the invention, I desire, therefore, that only such limitations shallbe placed thereon as are imposed by the' prior art.

I claim as my invention:

A1. In an electric furnace, the combination with a plurality of refractory walls enclosing a. furnace chamber, and an opening in one of ,said Walls, of a quickly removable heating unit located outside of said Wall and closely adjacent to said opening.

2. In an electric furnace, the combination with a pluarlity of refractory Walls enclosing a furnace chamber, and a plurality of openings in said walls, of a plurality of open-sided casin s, each having a heating unit therein, an operatively engaging the outside of said furnace structure and covering the respective openings.

3. In an electric furnace, the combination with a plurality of refractory Walls enclosing a furnace chamber, and a plurality of openings in said Walls, of a plurality of quickly removable heating uunit structures located outsideof, and in operative engagelng a furnace chamber, and an opening in one of sald Walls, of a qulckly removable open-sided casing located outside of, and in' operative engagement with, said Wall and over said opening, and a heating element inY said casing for radiating heat into said furl nace chamber.

5. In an electric furnace, the combination with a plurality of refractory Walls enclos- :ing a furnace chamber, and an opening in one of said Walls, of a heating unit structure comprising a heating element and a heatinsulating casing partially surrounding said element and operatively engaging one of said Walls and covering said opening.

6. In an electric furnace, the combination with a plurality of furnace walls enclosing a furnace chamber and comprising heat-insulating refractory material, and a plurality of spaced openings in said Walls, of a pluralitylof removable heating-unit structures, each comprising a heating element and a heat-insulating casing partially surrounding said element, operatively engaging said Walls and covering the respective openings, said heating elements being located 1n said casings to radiate heat into said furnace chamber. a

7. In anl electric furnace, the combination witha plurality of refractory Walls enclosing a furnace chamber, and an opening in ing a furnace chamber, and a plurality ofopenings in said Walls, said openings being distributed substantially uniformly around said chamber7 and a plurality of radiantl electric heating means o eratively associated with said furnace outsi e of-said Walls and effective to cause substantially uniform heating of material placed in said chamber.

` In testimony whereof, I have hereunto subscribed by name this 8th day of Marchl` esoneri M. LITTLE. 

